Sun is the primary source of Energy. The ultimate source of almost all forms of energy that we use today is the energy that comes from the Sun.
The Sun, is about 93 million miles away from the Earth. The sun provides us enormous amounts of energy in the form of solar radiation reaching the surface of the earth from a distance of 93 million miles in only 8 minutes.
The interior of the sun is supposed to be a temperature of 45 million degrees Fahrenheit and is in a gaseous state. At such a high temperature, hydrogen atoms fuse with helium to produce the energy that powers the planet earth.
The energy is electromagnetic in nature. Green plants use this solar energy to produce food. These plants are in turn, consumed by animals to get energy. The fossil fuels we use today are a form of solar energy stored millions of years ago in plant and other living things.